Can I use this service if I don't have a printer?

Yes, there are a number of options available to you. If you have access to a printer at work, or at a friend's house, you can step through the service, and then at a later date, go to another computer, login to your account and then print your document from that computer. If you don't want to login to your account from this computer, you can simply email your document to any email address; your own, or a friend's email address, and have them print it for you. This option is available to you from the MyWill main menu. The same options are available to you for the Power of Attorney service, and also the Living Will service.
If you would like to print your document at a public place, like a print shop, or a local library, then you can step through the service and then download and print your document as a PDF file. This can then be stored on a memory stick and you can then use a printing service to print your Will.
Finally, if you have no way of accessing any printer either through a friend, family member or community service, then login to your account, scroll to the bottom of your member home page, and then click on "Document Print and Ship". There is a small charge for this, but this service prints your document, puts it in a folder with signing instructions, and then sends the document out to you. You should receive it in a few days.